1. Field of the Invention
This invention pertains to a vertical form fill and seal machine, more particularly to the manufacture of reclosable containers or bags by the use of a transverse directional zipper with a double seal flange profile configuration.
2. Description of the Prior Art
In the prior art, it is known to use a form fill and seal machine to manufacture reclosable bags from a roll of film material by mounting transverse directional profile strip fastener assemblies onto the web of film material. It is further well known for the bags to be filled with foodstuffs or similar contents during the manufacturing process. It has been found, however, that the output rate of this manufacturing process may be constrained by the step of mounting of the transverse directional profile strip. More specifically, for a given zipper and film combination at specific seal temperatures and pressures, a minimum dwell time is required to attach a zipper segment to the film. Quite often this dwell time is the limiting factor in the ultimate cycle speed of the apparatus. In other cases, the speed at which the zipper can be delivered to the sealing area is the limiting factor.
The use of a profile strip with fasteners for adjacent bags, that is, the xe2x80x9csaddlebagxe2x80x9d concept is known. However, to make a xe2x80x9csaddlebagxe2x80x9d utilizing a zipper on the short side of the package, typically a horizontal form fill and seal machine (HFFS) is used. However, a second piece of equipment is typically required to collect the bags coming off of the machine, and thereafter to orient and seal the tops of the packages together. Similarly, with the use of a vertical form fill and seal machine (VFFS), the print on the web must be adjusted in order to compensate for every other bag being manufactured upside-down. Additionally, the manufacturing process is complicated by seal jaws being adapted to seal the web with and without the zipper profile, on alternate cycles.
Moreover, the registration of the edge of a single zipper with the cut-off knife in a form fill and seal machine has a tolerance of at least one sixteenth of an inch. This can result in the zipper extending into the cut area, causing a poor or incomplete cut, or it can result in the bag film extending above the edge of the zipper either resulting in a multitude of flanges for the consumer to grasp when opening the package or extra bag film being sealed above the zipper and making access to the zipper and its opening features difficult.
U.S. Pat. No. 5,951,453 entitled xe2x80x9cRecloseable Bag Assembly and Method of Making Samexe2x80x9d issued on Sep. 14, 1999 to Yeager discloses the placing of fastener profiles in adjacent pairs with a common flange. However, the placing of one of the thin elongated profile strips directly on the webbing can require increased complexity in the manufacturing process.
U.S. Pat. No. 4,528,224 entitled xe2x80x9cMethod of Making Multiple Reclosable Bag Materialxe2x80x9d issued on Jul. 9, 1985 to Ausnit relates to the fastener profile being applied in the machine direction, rather than the transverse direction, between two rolls of film.
It is therefore an object of this invention to provide a method of form fill and seal manufacture of reclosable bags which has increased manufacturing rates.
It is therefore a further object of this invention to provide a method of form fill and seal manufacture of reclosable bags which uses a plastic strip with adjacent pairs of fastener profiles in the transverse machine direction to provide the fastener profiles for two adjacent bags being manufactured.
It is therefore a still further object of this invention to provide a method of form fill and seal manufacture of reclosable bags which maintains a high degree of registration accuracy.
It is therefore a still further object of this invention to provide a method of form fill and seal manufacture of reclosable bags which accommodates the differences in sealing the upper and lower transverse portions of the reclosable bag.
It is therefore a still further object of this invention to provide the above objects while compensating the printing of the web for every other bag being manufactured upside-down.
It is therefore a final object of this invention to provide the above objects with a minimized requirement for additional equipment.
These and other objects are attained by providing preferably, a vertical form fill and seal device in which segments of a plastic zipper strip are oriented in a transverse direction to the length of a long web and are attached to the center of the web. The length of the segments is slightly less than one half of the width of the web. Each segment of plastic zipper strip includes two adjacent pairs of reclosable zipper profiles on flanges. The zippers are oriented on the strips such that the consumer side of each zipper pair faces the center of the strip and the product side faces the outside edge of the strip.
The strips may be secured to the web just prior to entering the form fill and seal device and fed directly into the form fill and seal device or, alternately, the web with the attached zipper segments is assembled at a site remote from the form fill and seal device and wound back up. At a later time, the rolled up web is put on the form fill and seal machine which forms the web into a tube.
Product is loaded into the tube formed by the web in the form fill and seal device and a seal is made across the tube transverse to the length of the tube (i.e., a cross seal) midway between zipper segments. The cross seal applies two parallel seals, and a knife cuts between the two seals thereby causing the two seals to form the bottoms of two separate bags. The web is indexed, product is filled into the tube and the cross-seal applies two parallel seals across the tube, collapsing the tube and sealing the inner surface of the tube to the exposed side of the zipper segment. A knife cuts between the two seals, and also cuts the zipper in half along its length, these seals and zipper segments thereby forming the tops of two separate bags.